A need exists for a heater than can heat large quantities of water that is relatively inexpensive in its construction and has good efficiency to reduce the costs of fuel for the heater and increase the speed of heating. One application for such a heater is for use with swimming pools of the inground or above ground type. An efficient heater permits the owner of the pool to extend its time of use when the weather turns cold.
Swimming pools have a large volume of water. For example, a mid-size above ground pool of 30' by 15' holds about 30,000 gallons. The heat required to heat the pool water to a usable temperature, usually about 85.degree., is a function of the water volume as well as the ambient temperature, the original temperature of the pool water and the desired final temperature. It is desired to perform the heating process in as short a time period as possible and at the minimum cost for fuel.
Heretofore, heaters such as for swimming pools have been provided which use electrical or gas fired heating elements. Such heaters are, in general, relatively inefficient. They are usually fixed in place and require a relatively long period of time to heat the water from an initial cool/cold temperature, where there basically has been no prior heating of the water and the ambient temperature is low, to one that is acceptable to the user. A fixed heater cannot be easily used with above ground pools, or used with different pools. Also, often it requires that a special housing be constructed for the heater.
Portable heaters have been used. In general, the available portable heaters have been relatively inefficient. The inefficiency results from a variety of factors such as, for example, excessive condensation as the cool water is being heated and a layout of the parts that does not result in maximum utilization of the heat from the source.